Do ants really count their steps?

Several years ago, scientists published an excellent study about how desert ants find their way home after foraging. The story got a lot of media attention; unfortunately, much of the coverage described the ants “counting steps”, which isn’t what the researchers reported and feeds into existing myths rather than broadening our scope. To explain what I think is wrong with that approach, I’m going to tell you a story about ants on stilts, body swapping and how we perceive space.

The actual study was quite straightforward. Unlike many other ants, Saharan desert ants (Cataglyphis fortis) don’t use chemical trails to navigate between their nest and a food source. Instead, they use a “path integrator” to calculate the direct route home after their meandering outward journey. Scientists knew that the ants used a compass based on sunlight to judge direction, but not how they determined the distance. Researchers had already shot down several ideas, like using visual cues or estimates of energy usage, so the team decided to test a very old idea: that the ants might be using the number of steps taken to reckon distance. The crucial experiment was to change the length of the returning worker’s steps by gluing pig bristles to their legs to artificially lengthen them. When this was done, the ants took longer strides and ended up overshooting their return trip. The converse experiment also worked: ants with shortened legs had a shorter stride and so overestimated how far they’d gone, stopping before they had reached the nest entrance. After spending a day in the nest, the ants had adjusted to their new legs and were able to make it out and back to the feeding site without any trouble. It was a really neat experiment and did a great job of showing that these ants calculate distance based on how many steps they’ve taken. The researchers called this a “step integrator” or “loosely speaking, a step counter, although the ants most probably do not literally count”.

So, what’s the problem? Unfortunately, a lot of the coverage of this story gives the impression the ants really are counting, which isn’t what the paper claimed. NPR wrote about it under the headline “Ants That Count!” while Livescience went with “When Ants Go Marching, They Count Their Steps“. To their credit, I think New Scientist actually covered the story quite well. A “step integrator” gives the ants a sense of distance based on how many steps they’ve taken, but that’s not the same as counting steps. Science writers always face the challenging task of simplifying a complex subject which is often full of nuances. There’s always the risk of oversimplifying, which not only does a disservice to readers but can also feed various social myths and constructs, including how special humans are and the onward march of progress. In this case, I think the simplified version draws from and supports the pervasive and enduring myth of a chain of being, with humans at the top and “lower” animals, little more than automata, at the bottom. In fact, at its core a step integrator might not be so different from the way we build our sense of time and space — which is where the body swapping comes in.

The neuroscientists at the Brain, Body and Self lab of the Karolinska Institute in Stockholm regularly make volunteers swap bodies with different kinds of dolls and mannequins to investigate our sense of self. In 2011, they decided to see what the world would look like from bodies that were much bigger or smaller than usual. Participants wore a headset which gave them a first person view of a doll’s body lying in the same position as them. They saw the leg of the doll being stroked at the same time as someone stroked their leg; the combination of touch and sight tricked their brain into thinking the doll’s body was their own. When the doll was threatened with a knife, participants unconsciously responded — breaking into a sweat and showing a change in skin conductance. As though body swapping wasn’t enough, the team wanted to see how this would affect the perception of size and distance. The participants consistently over- or under-estimated, depending on how big the doll was. People who had swapped bodies with a little Barbie doll thought they were in a world of giants, vastly overestimating how big or how far away everything was. Meanwhile, those who had swapped into 400cm tall bodies felt like they were giants, thinking everything was tiny and close by. This was true regardless of whether people estimated the distances verbally or tried to walk to an object while blind-folded. It turns out that our brains use our body size to measure space; when we look through the eyes of giants or Lilliputians, everything gets scaled up or down accordingly.

As the authors point out, the ants most probably aren’t literally counting their steps. Instead, the number of steps taken gives them a sense of how far they’ve travelled. The body swapping experiments show that humans do something similar, estimating distance based on the size of their body, and make the same kinds of mistakes when their stride length doesn’t match their expectations. Though the particulars of the mechanism might be very different, in both studies distance is estimated through some kind of sensation of a body — whether it’s based on stride length or body size. Yet we persist in describing many organisms as simple automata, sensing and counting and responding, while reserving “awareness” for ourselves. This viewpoint informs how we approach the world around us, as well as how we conduct and report science. I disagree with it and am glad to see mounting evidence for unexpected faculties in other organisms. I have no idea how self-aware an ant is, but the findings fit with the possibility that they are aware of their body size and stride length, which they use to estimate distance. To me, that’s a far more exciting and interesting take on the story, broadening our conception of other organisms and their own unique perspective, rather than reinforcing our illusions of superiority and dominance.

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64 thoughts on “Do ants really count their steps?”

I absolutely agree with your take on body awareness, whether with ants or any other species. I think we give nature’s creatures far too little credit for their “intelligence,” both innate and learned. I have a very poor sense of direction – I would love to have the desert ants’ “step integrator!”

Very interesting. I am probably one of those writers (more interpretive than scientific) that is guilty of over-simplification from time to time…mostly because I am usually limited to only a few sentences to get across ideas, and also because I have to write for the general public, which often means fifth – ninth grade levels. But, I try to err in the opposite direction…giving other living creatures more credit for being complex living beings, rather than merely placing them below humans. It’s tricky, and subtle, but important. Thanks for your thoughtful take on the matter.

I’m glad to hear that you err on the side of over-estimating other creatures, if only because that matches the way I see the world.🙂 It’s certainly not easy to write for a general audience — trying to strike a balance somewhere between too much information and oversimplification. I think I’ve gotten better at it since starting this blog, but it’s still a challenge.

Great article. I’m a fellow scientist-turned-writer so your perspective is not dissimilar to my own.

I’m currently writing a story about ants for a short-story fiction collection. It’s really useful to understand more about how they use sunlight and this ‘inner compass’ to track their return journey – and, the rest of your article gives me plenty of new insights, too!

I follow a few other cool science folks on WP and even attempted a short fun physics article recently, which has, weirdly for me, been very popular with people searching my blog. It’s called ‘Massive Equation’ . . . hope you’ll take a peek if you get time.

Thanks for this post and keep up work on your informative, unique blog.

Good question. The ants don’t just take the same number of steps on the way back as on the way out. They use a “path integrator” to add up all the twists and turns on the outwards journey and get an idea of their current position; based on that, they figure out the straight line path back home and use the length of that to figure out how far they have to walk.

Very interesting story. Definetly,they have their own world like us, but more organized. I always found interesting the live of the ants. You know one of the first scientific curiosity that I had was with the ants. I remember when I was five years old , that I was watching the wall of my bedroom with many ants walking making a long line on th wall, and I asked to my grandmother: “Why the ants touch when they saw another ant in its way?” And my grandmother told me smiling:” They have to pass the message, that we have to continuing working, and never stop to maintain our world.”

I heard the NPR report you refer to years ago and actually wrote a scene in my novel-in-progress where I have two characters discussing this idea of ants counting steps, so I’m very happy to find this post and get more info! Thanks!

Fascinating! I work in the arts and your article is a great springboard for a creative project! I know I feel something similar when I have to drive a different car… it must be much worse if one is reacting to a different body image.

Brilliant! I also believe that we’re not really dominant of everything in the world; stupid notion. Everything has it’s own intellect and soul, and the thought that we’re “god’s almighty un-animalistic golden children” (not really quoting anybody), is quiet retarded. We co-exist with creatures on this planet, and we need to take mesures to be more humane and loving of other creatures.

Thanks for that post, and do me a favor and check out my blog please.
Thanks!

Wonderful! Thank you for sharing–very informative, interesting, and I agree with you completely about humans not being “set apart.” We are different from other animals. And ants are too. And horses are too. And sea bass are too. And also we’re all alike. Love everything about this post.❤

Congrats on being freshly pressed… lovely post. ever since I saw the movie ‘ANTS LIFE ‘ … I always thinks about ants … even ‘Honey I Shrunk The Kids… Hee Hee… Since then I always feel for these creatures … small ones poor thingies… :)))) Cheers…!!!

Well, one reason to care is the simple thrill of solving a puzzle and discovering how something works; another is the pleasure of understanding the world around us. Those are my motivations for reading about, practising and communicating science.

On the other hand, I understand that not everyone enjoys research for its own sake. If you’d like to see some kind of application for research like this, here’s a story about how understanding gecko feet has helped us build a robot that can climb straight up walls. There’s also this blog post about robots with ant-like navigation systems. So even if basic science isn’t your thing, I think there’s plenty of reason to care about this.

Of course, if you’re not interested in basic science or its application to manipulate the world around us (ie, technology), then you probably won’t care about this. But if that’s the case, why are you reading a science blog?

I just wanted to tell you I enjoyed the post at the time that I read it when it was first Freshly Pressed, and it came to mind again today almost 2 weeks later, so I think that means it was quite a good post. Thanks!

I didn’t say anyone claimed that ants “count like we do”. I said that many articles give the impression that ants count their steps to measure distance and linked to examples. The NPR article says “In other words, all the ants counted the same number of steps back!” and “This experiment strongly suggests that ants do have internal pedometers that allow them to ‘count’ their way home.”, while the article at LiveScience claims the experiment tested whether ants were “counting off steps with an internal pedometer.”

It’s certainly possible that some kind of “internal counter” keeps track of how many steps the ants take and uses that to measure distance. However, I’m highlighting another possibility — that, just like humans, ants have an awareness of distances (and maybe other measurements in the world around them) based on how big they think their body is. The first explanation is more mechanistic; it probably feels better to people who tend to view other animals as automatons or view the natural world as some kind of grand hierarchy. That’s not my view of the world, though, and the explanation I’ve suggested is consistent with the data in this paper.

Also, “the findings fit with the possibility that they are aware of their body size and stride length, which they use to estimate distance.” Totally wrong; if they were aware of their body size, and stride length they wouldn’t have misgauge distance after the leg-length manipulation.

Actually, if they’re using stride length to estimate distances and we change the length of their step, I would expect them to miscalculate. That’s precisely what humans did when the actual size of their “body” didn’t match what they imagined it to be. That’s why I put these two pieces of research together. Sure, if the ants updated their imagined stride length after having bits glued to them, they wouldn’t misjudge distances — but that’s not the argument I’m making. I’m saying that the results in this study are compatible with (at least) two possible explanations: (1) the ants are measuring distance by counting steps or (2) the ants use their body as a measuring stick for the world (as we do) and get confused when their body is bigger or smaller than they imagine it to be.

The problem I have with this idea is that the opposite was observed in experiment; ants that were made larger (stilted) traveled a greater distance back and ants that were made smaller (legs cut) traveled a shorter distance back. If confused about their size in the way you describe, their behavior should have been the opposite. A counting mechanism makes more sense to me.

Your interpretation might be true if the ants were aware of their new body size. That’s what happened with humans — people who thought their body was huge (when it was actually just human-sized) underestimated the distance. The difference is that in that experiment the human’s body size didn’t change while their conception of it did; in the case of the ants, their body actually changed size, while (I’m suggesting) their conception of it didn’t. To compare the two experiments, you need to consider ants with stilts alongside humans tricked into thinking they’re doll-sized. In both cases, the actual body size is bigger than imagined, with the result that the ant/human covers a greater distance than they expected.

Reblogged this on synkroniciti and commented:
This is an outstanding article which speaks to the awareness of ants and how they use their own body size to determine distance. Fascinating read from Inspiring Science.